人不可貌相，海水不可斗量 (rén bù kě mào xiāng, hǎi shuǐ bù kě dǒu liáng)

人不可貌相，海水不可斗量

(rén bù kě mào xiāng, hǎi shuǐ bù kě dǒu liáng)
English Translation: “People cannot be judged by their appearance, just as the sea cannot be measured.”

Meaning:
This is equivalent to “don’t judge a book by its cover.” It reminds us not to judge others based on their outward appearance, as there’s always more than meets the eye.

Example:
虽然他看起来很普通，但人不可貌相，海水不可斗量，他其实非常聪明和有才华。
(Although he appears ordinary, “people cannot be judged by their appearance, just as the sea cannot be measured.” He is actually very smart and talented.)

Source: Hello Mandarin